Dispersion-Induced-Loss-Independent Photonic Instantaneous Frequency Measurement Using Remote-Fiber-Based Tunable Microwave Filter

A photonic approach to the instantaneous frequency measurement (IFM) of a remote microwave receiver is proposed and experimentally demonstrated. In the proposed system, two continuous-wave light waves having a tunable wavelength spacing are distributed to a remote unit. After being phase-modulated by a received microwave signal, the two light waves are fed back to the indoor unit via a length of single-mode fiber which serves as a remote link and a delay line to establish a two-tap microwave filter. The microwave frequency to be measured is then estimated from the filtering response that is obtained by removing the dispersion-induced loss in the fiber-link. Therefore, a dispersion-induced-loss-independent approach is established which enables a flexible and distributed IFM solution for remote receivers.